This invention relates to novel fluorinated organosilicon compounds useful as a crosslinking agent for addition reaction.
Rubber compositions of the addition reaction curing type generally contain a base polymer having alkenyl groups such as vinyl groups, a compound having hydrogen atoms directly attached to silicon atoms (i.e., SiH groups), and an addition reaction catalyst such as a platinum group catalyst. Cure takes place through the addition of the SiH groups to the alkenyl groups on the base polymer.
Organosilicon compounds having SiH groups are known in the art. For example, JP-A 3-197484 discloses an organosilicon compound of the structure that a SiH group is attached to a silicon atom having a fluoroalkyl substituent through an oxygen atom, as shown by the following formula. 
This compound is capable of hydrosilylation reaction with vinyl group-bearing compounds, and it is a useful raw material from which various derivatives are synthesized. For example, modifiers, crosslinking agents for resins and rubber, surfactants, and additives can be synthesized from this compound.
However, the use of this compound as a crosslinking agent gives rise to the problem that the compound is likely to volatilize upon curing at elevated temperatures so that cured properties become unstable.
A compound of the following formula is also known. 
When this compound is used as a crosslinking agent in a composition comprising as a base polymer a polymer having a high fluorine content such as perfluoropolyether, the composition lacks storage stability and cure stability because of poor compatibility between the components.
An object of the invention is to provide a novel fluorinated organosilicon compound having SiH groups capable of hydrosilylation reaction with such compounds as vinyl group-bearing fluoro-polymers in a stable manner and fully compatible therewith.
We have found that a fluorinated organosilicon compound having at least one fluorinated organic group and at least three SiH groups in a molecule as shown by the general formula (1) below is capable of hydrosilylation reaction with such compounds as vinyl group-bearing fluoro-polymers in a stable manner and is fully compatible with such polymers.
The invention provides a fluorinated organosilicon compound having the following general formula (1). 
Herein R1 is independently a monovalent hydrocarbon group having 1 to 6 carbon atoms; X is independently xe2x80x94CH2xe2x80x94, xe2x80x94CH2Oxe2x80x94, xe2x80x94CH2OCH2xe2x80x94 or xe2x80x94Yxe2x80x94NR2xe2x80x94COxe2x80x94 wherein Y is xe2x80x94CH2xe2x80x94 or a divalent group of the following structural formula (I): 
and R2 is hydrogen or a monovalent hydrocarbon group having 1 to 10 carbon atoms; Rf1 is a monovalent perfluoroalkyl or perfluorooxyalkyl group; Z is a divalent hydrocarbon group of 1 to 15 carbon atoms which may contain an ether bond; subscripts a, b, c and d are integers satisfying axe2x89xa63, bxe2x89xa63, cxe2x89xa63, dxe2x89xa63, 3xe2x89xa6a+cxe2x89xa65, 1xe2x89xa6b+dxe2x89xa63, a+bxe2x89xa63, and c+dxe2x89xa63, and e is independently 0 or 1.